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Reports on Progress in Physics

H R Glyde
Progress made in measuring and interpreting the elementary excitations of superfluid and normal liquid [Formula: see text] in the past 25 years is reviewed. The goal is to bring up to date the data, calculations and our understanding of the excitations since the books and reviews of the early 1990s. Only bulk liquid [Formula: see text] is considered. Reference to liquid [Formula: see text], mixtures, reduced dimensions (films and confined helium) is made where useful to enhance interpretation. The focus is on the excitations as measured by inelastic neutron scattering methods...
November 23, 2017: Reports on Progress in Physics
Peter Woelfle
Quasiparticles are a powerful concept of condensed matter quantum theory. In this review the appearence and the properties of quasiparticles are presented in a unifying perspective. The principles behind the existence of quasiparticle excitations in both quantum disordered and ordered phases of fermionic and bosonic systems are discussed . The lifetime of quasiparticles is considered in particular near a continuous classical or quantum phase transition, when the nature of quasiparticles on both sides of a transition into an ordered state changes...
November 20, 2017: Reports on Progress in Physics
Dragan Huterer, Daniel L Shafer
The discovery of the accelerating universe in the late 1990s was a watershed moment in modern cosmology, as it indicated the presence of a fundamentally new, dominant contribution to the energy budget of the universe. Evidence for dark energy, the new component that causes the acceleration, has since become extremely strong, owing to an impressive variety of increasingly precise measurements of the expansion history and the growth of structure in the universe. Still, one of the central challenges of modern cosmology is to shed light on the physical mechanism behind the accelerating universe...
November 9, 2017: Reports on Progress in Physics
S Cocco, Christoph Feinauer, Matteo Figliuzzi, Remi Monasson, Martin Weigt
In the course of evolution, proteins undergo important changes in their amino-acid sequences, while their three-dimensional folded structure and their biological function remain remarkably conserved. Thanks to modern sequencing techniques, sequence data accumulate at unprecedented pace. This provides large sets of so-called homologous, i.e.~evolutionarily related protein sequences, to which methods of inverse statistical physics can be applied. Using sequence data as the basis for the inference of Boltzmann distributions from samples of microscopic configurations or observables, it is possible to extract information about evolutionary constraints and thus protein function and structure...
November 9, 2017: Reports on Progress in Physics
Sigitas Tamulevicius, Sarunas Meskinis, Tomas Tamulevičius, Horst-Guenter Rubahn
In this work we present an overview on structure formation, optical and electrical properties of diamond like carbon (DLC) based metal nanocomposites deposited by reactive magnetron sputtering and treated by plasma and laser ablation methods. The influence of deposition mode and other technological conditions on the properties of the nanosized filler, matrix components and composition were studied systematically in relation to the final properties of the nanocomposites. Applications of the nanocomposites in the development of novel biosensors combining resonance response of wave guiding structures in DLC based nanocomposites as well as plasmonic effects are also presented...
October 27, 2017: Reports on Progress in Physics
Uri Obolski, Yoav Ram, Lilach Hadany
Adaptive landscapes represent a mapping between genotype and fitness. Rugged adaptive landscapes contain two or more adaptive peaks: allele combinations with higher fitness than any of their neighbors on the genetic space. How would a population evolve on such rugged landscapes? Evolutionary biologists have struggled with this question since it was first introduced in the 1930's by Sewall Wright. Discoveries in the fields of genetics and biochemistry inspired various mathematical models of adaptive landscapes...
October 20, 2017: Reports on Progress in Physics
Hartmut Sadrozinski, Abraham Seiden, Nicolo Cartiglia
The evolution of particle detectors has always pushed the technological limit in order to provide enabling technologies to researchers in all fields of science. One archetypal example is the evolution of silicon detectors, from a system with a few channels 30 years ago, to the tens of millions of independent pixels currently used to track charged particles in all major particle physics experiments. Nowadays, silicon detectors are ubiquitous not only in research laboratories but in almost every high tech apparatus, from portable phones to hospitals...
October 20, 2017: Reports on Progress in Physics
Suzanne Staggs, Lyman Page, Joanna Dunkley
Measurements of the anisotropies in the Cosmic Microwave Background (CMB) radiation have provided a wealth of information about the cosmological model that describes the contents and evolution of the universe. These data have led to a standard model described by just six parameters. In this review we focus on discoveries made in the past decade from satellite and ground-based experiments, and look ahead to those anticipated in the coming decade. We provide an introduction to the key CMB observables including temperature and polarization anisotropies, and describe recent progress towards understanding the initial conditions of structure formation, and establishing the properties of the contents of the universe including neutrinos...
October 20, 2017: Reports on Progress in Physics
Andrew J A James, Robert M Konik, Philippe Lecheminant, Neil Robinson, Alexei M Tsvelik
We review two important non-perturbative approaches for extracting the physics of low- dimensional strongly correlated quantum systems. Firstly, we start by providing a comprehensive review of non-Abelian bosonization. This includes an introduction to the basic elements of confor- mal field theory as applied to systems with a current algebra, and we orient the reader by presenting a number of applications of non-Abelian bosonization to models with large symmetries. We then tie this technique into recent advances in the ability of cold atomic systems to realize complex symme- tries...
October 9, 2017: Reports on Progress in Physics
Robert Marsland Iii, Jeremy England
The past twenty years have seen a resurgence of interest in nonequilibrium thermodynamics, thanks to advances in the theory of stochastic processes and in their thermodynamic interpretation. Fluctuation theorems provide fundamental constraints on the dynamics of systems arbitrarily far from thermal equilibrium. Thermodynamic uncertainty relations bound the dissipative cost of precision in a wide variety of processes. Concepts of excess work and excess heat provide the basis for a complete thermodynamics of nonequilibrium steady states, including generalized Clausius relations and thermodynamic potentials...
October 4, 2017: Reports on Progress in Physics
Regina Hoffmann-Vogel
Insulating substrates allow for in-plane contacted molecular electronics devices where the molecule is in contact with the insulator. For the development of such devices it is important to understand the interaction of molecules with insulating surfaces. As substrates, ionic crystals such as KBr, KCl, NaCl and CaF$_2$ are discussed. The surface energies of these substrates are small and as a consequence intrinsic properties of the molecules, such as molecule-molecule interaction, become more important relative to interactions with the substrates...
September 29, 2017: Reports on Progress in Physics
Philippe Brax
Explaining the origin of the acceleration of the expansion of the Universe remains as challenging as ever. In this review, we present different approaches from dark energy to modified gravity. We also emphasize the quantum nature of the problem and the need for an explanation which should violate Weinberg's no go theorem. This might involve a self-tuning mechanism or the acausal sequestering of the vacuum energy. Laboratory tests of the coupling to matter of nearly massless scalar fields, which could be one of the features required to explain the cosmic acceleration, are also reviewed...
September 22, 2017: Reports on Progress in Physics
Krzysztof Sacha, Jakub Zakrzewski
Time crystals are time-periodic self-organized structures postulated by Frank Wilczek in 2012. While the original concept was strongly criticized, it stimulated at the same time an intensive research leading to propositions and experimental verifications of discrete (or Floquet) time crystals -- the structures that appear in the time domain due to spontaneous breaking of discrete time translation symmetry. The struggle to observe discrete time crystals is reviewed here together with propositions that generalize this concept introducing condensed matter like physics in the time domain...
September 8, 2017: Reports on Progress in Physics
Robert P Johnson
The use of hadron beams, especially proton beams, in cancer radiotherapy has expanded rapidly in the past two decades. To fully realize the advantages of hadron therapy over traditional X-ray and gamma-ray therapy requires accurate positioning of the Bragg peak throughout the tumor being treated. Already a half century ago suggestions were made to use protons themselves to develop images of tumors and surrounding tissue, to be used for treatment planning. The recent global expansion of hadron therapy coupled with modern advances in computation and particle detection has led several collaborations around the world to develop prototype detector systems and associated reconstruction codes for proton computed tomography (pCT) as well as more simple proton radiography, with the ultimate intention to use such systems in clinical treatment planning and verification...
September 8, 2017: Reports on Progress in Physics
Helen Miller, Zhaokun Zhou, Jack Shepherd, Adam Wollman, Mark Leake
Single-molecule biophysics has transformed our understanding of biology, but also of the physics of life. More exotic than simple soft matter, biomatter lives far from thermal equilibrium, covering multiple lengths from the nanoscale of single molecules to up several orders of magnitude to higher in cells, tissues and organisms. Biomolecules are often characterized by underlying instability: multiple metastable free energy states exist, separated by levels of just a few multiples of the thermal energy scale kBT, where kB is the Boltzmann constant and T absolute temperature, implying complex inter-conversion kinetics in the relatively hot, wet environment of active biological matter...
September 4, 2017: Reports on Progress in Physics
Yun-Yi Pai, Anthony Tylan-Tyler, Patrick Irvin, Jeremy Levy
1 Overview 1 1.1 Introduction 1 1.1.1 Oxide growth techniques are rooted in search for high-Tc superconductors 2 1.1.2 First reports of interface conductivity 2 1.2 2D physics 2 1.3 Emergent properties of oxide heterostructures and nanostructures 3 1.4 Outline 3 2 Relevant properties of SrTiO3 3 2.1 Structural properties and transitions 3 2.2 Ferroelectricity, Paraelectricity and Quantum Paraelectricity 4 2.3 Electronic structure 5 2.4 Defects 6 2...
August 30, 2017: Reports on Progress in Physics
Abhay Ashtekar
Most of the literature on general relativity over the last century assumes that the cosmological constant [Formula: see text] is zero. However, by now independent observations have led to a consensus that the dynamics of the universe is best described by Einstein's equations with a small but positive [Formula: see text]. Interestingly, this requires a drastic revision of conceptual frameworks commonly used in general relativity, no matter how small [Formula: see text] is. We first explain why, and then summarize the current status of generalizations of these frameworks to include a positive [Formula: see text], focusing on gravitational waves...
August 29, 2017: Reports on Progress in Physics
Manabendra Nath Bera, Antonio Acín, Marek Kuś, Morgan W Mitchell, Maciej Lewenstein
This progress report covers recent developments in the area of quantum randomness, which is an extraordinarily interdisciplinary area that belongs not only to physics, but also to philosophy, mathematics, computer science, and technology. For this reason the article contains three parts that will be essentially devoted to different aspects of quantum randomness, and even directed, although not restricted, to various audiences: a philosophical part, a physical part, and a technological part. For these reasons the article is written on an elementary level, combining simple and non-technical descriptions with a concise review of more advanced results...
December 2017: Reports on Progress in Physics
David M Richards, Robert G Endres
Phagocytosis is a fascinating process whereby a cell surrounds and engulfs particles such as bacteria and dead cells. This is crucial both for single-cell organisms (as a way of acquiring nutrients) and as part of the immune system (to destroy foreign invaders). This whole process is hugely complex and involves multiple coordinated events such as membrane remodelling, receptor motion, cytoskeleton reorganisation and intracellular signalling. Because of this, phagocytosis is an excellent system for theoretical study, benefiting from biophysical approaches combined with mathematical modelling...
December 2017: Reports on Progress in Physics
C J A P Martins
The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete-if not incorrect-and that new physics is out there, waiting to be discovered. A key task for the next generation of laboratory and astrophysical facilities is to search for, identify and ultimately characterize this new physics. Here we highlight recent developments in tests of the stability of nature's fundamental couplings, which provide a direct handle on new physics: a detection of variations will be revolutionary, but even improved null results provide competitive constraints on a range of cosmological and particle physics paradigms...
December 2017: Reports on Progress in Physics
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